Anthony Edwards of "ER"

NBC

For a show that' was on 15 years, it had its fair share of exits -- from George Clooney in season five to Noah Wyle in season 11, and the last season Maura Tierney and Mekhi Phifer. But Anthony Edwards was there from the beginning and when he said goodbye after his character (Dr. Mark Greene) died of a brain tumor, it was hard to imagine the show going on, but it did. When the series ends this year, it will be the longest-running American primetime medical drama of all time.

For a show that' was on 15 years, it had its fair share of exits -- from George Clooney in season five to Noah Wyle in season 11, and the last season Maura Tierney and Mekhi Phifer. But Anthony Edwards was there from the beginning and when he said goodbye after his character (Dr. Mark Greene) died of a brain tumor, it was hard to imagine the show going on, but it did. When the series ends this year, it will be the longest-running American primetime medical drama of all time.